Iran is still a "perilous" place for foreign companies to do business because of sanctions unaffected by the recent interim nuclear deal, a senior US administration official said on Wednesday during a visit to Rome.

The six-month agreement only provides for the easing of limited sanctions and the unblocking of some frozen Iranian assets abroad and foreign firms should not "over-interpret" its scope, the official said.

"Businesses need to take into account the legal and reputational risk of doing business with Iran," he said, speaking on condition of anonymity. (AFP)